One-way or overrunning clutches are used in a variety of power transmission applications. Bicycles, scooters, motorcycles, and automobiles all can have one or more overrunning clutches. The overrunning clutch transmits torque in one rotary driving direction but not the other. In some automotive applications, pawls are used as the element between two rotary parts of the clutch that transmit torque in one direction or the other. The pawls are held in one race and the other race has teeth that at least one or more of the pawls engage in one direction of relative rotary motion between the races (the driving direction) but not in the other direction (the free wheeling direction). The pawls are typically biased using an accordion or compression spring in the front of the pawl that biases it into the engaged position with the teeth.
This design requires much attention to the design of the pawl to make a clutch that allows the pawls to remain assembled in one race in the absence of the other race that normally keeps the pawls assembled to the one race. Overrunning clutches for bicycles sometimes use a rearward biasing of the pawls using a garter spring that fits within a groove that is provided in the pawls at an engagement angle. This is a costly method in biasing pawls, but reduces the total number of parts of the final assembly.
Rearward biasing by the springs in a pawl-type overrunning clutch allows designers more flexibility in the design of pawls. While accordion spring-type clutches that bias the pawls to an engagement position under the front portion of the pawl are inexpensive to manufacture, care must be taken in how the pivot point and the rear of the pawl pocket are designed if the pawls are required to remain assembled when the toothed race is removed.